<h2>DESCRIPTION</h2>

<em>r3.stats</em> calculates volume statistics for 3D raster maps.
Volumes are created on base of value subranges or groups of equal values.
The default number of subranges is 20 and can vary from 1 to infinite. 
Larger number of subranges will result in larger memory consumption.
The volumes are calculated in qubic meters. Null values are marked with "*".
If the flag <em>-e</em> is set, the number of subranges will be ignored.

<h2>NOTES</h2>

As with most GRASS 3D raster map modules, <em>r3.stats</em> operates on the cell
array defined by the current 3D region settings, not the original extent and
resolution of the input map. See <em>g.region</em>.
<p>The region setting will not effect the memory consumption of this module.
The number of subranges in case of value range calculation or the number of 
equal value groups effect the memory consumption and the calculation time.
The user can expect a huge time consumption to calculate the equal value
groups (flag <em>-e</em>) if large region settings occur for maps which
have many equal value groups (> 100000).

<h2>EXAMPLES</h2>
<h3>Lausanne FOSS4G 2006 3D demo dataset example</h3>

The 3D raster map <em>geology</em> has three values. Each value represents 
a specific geological layer, clay = 1, sand = 2 and bedrock = 3. To calculate
the volume of each geological layer, we can use the flag <em>-e</em> to group
equal values into single volumes. 
<em>r3.stats geology -e</em> will produce the following output:

<p><div class="code"><pre>
  num   |        value       |     volume    |   perc  |    count
      1             1.000000   300822000.000   50.13700        50137
      2             2.000000   101400000.000   16.90000        16900
      3             3.000000   197778000.000   32.96300        32963
      4                    *           0.000   0.00000            0

Number of groups with equal values: 3
Sum of non Null cells:
        Volume = 600000000.000
        Percentage = 100.000
        Count = 100000

Sum of all cells:
        Volume = 600000000.000
        Percentage = 100.000
        Count = 100000

</pre></div>
<h3>Generic example</h3>

<div class="code"><pre>
#create a small 3D region
g.region n=1000 s=0 e=2000 w=0 t=300 b=0 res3=100

#create a raster3D map with row() and null values
r3.mapcalc "volmap = if(row() == 5, null(), row())"

#run r3.stats with a subrange of 10
r3.stats input=volmap nsteps=10

#the result should look like this
 num   | minimum <= value   | value &lt; maximum    |     volume    |   perc  | cell count
      1          1.000000000          1.900000000    60000000.000   10.00000           60
      2          1.900000000          2.800000000    60000000.000   10.00000           60
      3          2.800000000          3.700000000    60000000.000   10.00000           60
      4          3.700000000          4.600000000    60000000.000   10.00000           60
      5          4.600000000          5.500000000           0.000   0.00000            0
      6          5.500000000          6.400000000    60000000.000   10.00000           60
      7          6.400000000          7.300000000    60000000.000   10.00000           60
      8          7.300000000          8.200000000    60000000.000   10.00000           60
      9          8.200000000          9.100000000    60000000.000   10.00000           60
     10          9.100000000         10.000000001    60000000.000   10.00000           60
     11                    *                    *    60000000.000   10.00000           60

Sum of non Null cells:
        Volume = 540000000.000
        Percentage =  90.000
        Cell count = 540

Sum of all cells:
        Volume = 600000000.000
        Percentage = 100.000
        Cell count = 600
</pre></div>

<h2>SEE ALSO</h2>

<em>
<a href="g.region.html">g.region</a>,
<a href="r3.univar.html">r3.univar</a>,
<a href="r.stats.html">r.stats</a>,
<a href="r.statistics.html">r.statistics</a>,
<a href="v.univar.html">v.univar</a>
</em>


<h2>AUTHOR</h2>
S&ouml;ren Gebbert

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